Typically, wet rooms in buildings are provided with a floor drain. The drain will include a pipe that extends through the floor with the upper end of the pipe being provided with a floor waste. The floor waste includes a tubular portion that projects into the pipe and an upper grid or grate that is generally located at floor level and through which water enters the tubular portion for delivery to the pipe.
The pipe at a position slightly below the floor waste may have an “S” bend which retains water to prevent gases passing up through the pipe to exit via the floor waste into the room.
A disadvantage of the above discussed floor waste is that, should the “S” bend become dry or be absent, the room is in direct communication with the sewer system.